The invention relates to an instrument for making at least one stripe-shaped transmural lesion in one or more walls of the atria of the heart, which lesion essentially blocks the electrical impulse conduction in a direction crosswise to the stripe-shaped transmural lesion.
All kinds of heart arrhythmias, and in particular chronic and paroxysmal atrial fibrillation, can currently be treated by surgery.
A known surgical procedure (MAZE) was designed to eliminate atrial fibrillation permanently. In this procedure incisions are made with a scalpel in the walls of the atria, in order to block, by the thus formed interruption of the tissue continuity electrical impulse conduction in a direction crosswise to the incisions. As a result of the subsequent scarring, these electrical blocks acquire a permanent character.
This known technique is as yet performed only to a limited extent worldwide, owing co the complexity of the operation. The increased risk is particularly associated with the duration of the operation and the way in which the operation has to be carried out.
The duration of the operation, and in particular the cross-clamp time (x-clamp) is so long that there is a great risk of damage to the heart muscle.
The cross-clamp time required for the MAZE procedure alone is currently still an average of 68 min. (range 50-102 min.), and the necessary time on the heart-lung machine is on average 182 min. (range 130-256 min.). For further data you are referred to Atrial Fibrillations: Mechanisms and Therapeutic Strategies, Futura Publishing Co. Inc. Armonk, N.Y. 1994. J. L. Cox: Surgical Interruption of Atrial Reentry as a Cure for Atrial Fibrillation. The way in which the operation is performed with the scalpel produces an increased risk of vascular suture leaks and subsequent bleeding, due to the large number and location of the vascular sutures involved.
The object of the present invention is to provide instrument of the abovementioned type which eliminates the abovementioned disadvantages, and which in particular shortens the time required for the operation and reduces the risk of bleeding and damage, therefore reducing the risk for the patient in open-heart surgery.
According to the invention, the instrument indicated is characterized in that the instrument is a probe in which the end which during the operation comes into contact with the wall to be treated is a closed electrode which can interact with an RF power source, while the Probe is of a relatively rigid type.
The instrument according to the invention is a probe by means of which in open-heart surgery it is possible to make a permanent change in an atrial wall which is transmural, i.e. it extends over the entire thickness of the wall.
As will be discussed at a later stage, during the performance of the operation the electrode at the end of the probe is brought into contact with the atrial wall to be treated and is moved along it in a linear pattern. On excitation of the electrode with RF power, dielectric (RF) heating of the wall tissue occurs. The RF treatment produces a change in the cell structure of the atrial wall, with the result that electrical impulse conduction in a direction crosswise to the transmural lesion is blocked.
In order to be able to work well with it, the probe must be of a relatively rigid type, so that the electrode can be accurately positioned on and moved along the atrial wall. In the operation no disintegration of the tissue of the atrial wall occurs, and there is no risk of subsequent bleeding. The operation can be carried out on the outside or the inside of the atrium as desired.
Methods of RF heating or dielectric heating are based on the use of heat generated in materials which are relatively poor electrical conductors when they are placed in high-frequency electromagnetic fields. The heat is generated as a result of dielectric losses occurring in a material situated between metal electrodes which form a capacitor which is connected to a high-frequency (RF) generator. Such heating is highly uniform and therefore extremely suitable for use of the instrument, the probe, according to the invention. During use of the probe, one of the capacitor xe2x80x9cplatesxe2x80x9d is formed by the electrode at the end of the probe, while the other xe2x80x9cplatexe2x80x9d is a counter-electrode which is stuck on, for example, the patient""s back; when the latter electrode is being placed, it is preferable to use a contact gel which has electrical conductance. Of course, the counter-electrode can also be placed on the outside of the atrial wall of the heart, for example if the electrode of the probe is being brought into contact with the inside of said wall.
In connection with the invention, reference is made to WO 95/03742, which discloses a catheter comprising at the distal a metal electrode by means of which tissue erosion, also known as ablation, can be carried out.
Such a catheter typically has a length of approximately 1 meter, a diameter of approximately 2 mm, and has an electrode of approximately 2 mm diameter, and its low thickness makes it very flexible, so that it can follow a blood vessel without any problems. This catheter is suitable for local punctate ablation. Such a catheter is not suitable for use as a probe for making stripe-shaped transmural lesions in an atrial wall.
In particular, the probe according to the invention has at least a handle; an end; a relatively rigid shaft between the handle and the end, and connecting and conduction means for connecting the end of the probe to an RF power source.
In the instrument according to the invention a temperature recorder is advantageously present near the end of the probe, which temperature recorder, operating in a feedback system with the RF power source, can regulate the temperature of the end of the probe to a preset value. Through input of the RF power, the temperature of the end of the probe will generally rise; feedback with the RF power source makes it possible to ensure that the temperature of the end does not exceed a predetermined value.
With use of RF power it is extremely important that the fewest possible electrical blockages should be present in the body section between the end of the probe and the counter-electrode on the outside of the body. On account of this, it is preferable to ensure that the probe can interact with means for supplying a physiologically acceptable liquid to the end thereof. In its simplest form, such a liquid is supplied near the electrode of the probe by way of a line which does not form part of the probe. The function of the liquid is, on the one hand, to cool the electrode and, on the other, to prevent the occurrence of electrically insulating air gaps. which adversely affect the efficiency of the RF action.
It is very advantageous for the probe according to the invention itself to have means for discharging a physiologically acceptable liquid near the end of the probe. Said liquid will generally preferably have a certain degree of electrical conduction, and is expediently a physiological salt solution.
In a very attractive embodiment, the instrument has between the handle of the probe and the shaft inlet means for introducing the physiologically acceptable liquid, which inside the shaft remains electrically insulated from the connecting and conduction means present in the shaft, while near the end it has outflow means for the physiologically acceptable liquid. With this embodiment, the functioning of the probe can be improved yet further, and it can be ensured that the greatest RF energy effect is concentrated in the wall of the atrium to be treated, forming the desired transmural lesion.
At the side of the handle facing away from the end of the probe, the conduction and connecting means of the probe according to the invention comprise a connector connected thereto, with contact means for connection of the electrode to the end of the probe and the temperature recorder present therein to the RF power source.
The connector is preferably of the rapid coupling type, so that easy coupling to the RF power source is permitted.
In order to make handling of the instrument according to the invention, in the form of a probe, as easy as possible for the operating surgeon during an open-heart operation, the shaft of the probe preferably has an intrinsic curvature, which is expediently approximately 140xc2x0.